After being forced to pose holding a piece of metal tubing while a police officer took a picture, saying "a photo for the memory books", he was allowed to go on to the bus.

As he did so, another officer kicked him in the leg.

In a statement later, police apologized for the "inadmissible action" and said they were launching an investigation.

Three protesters have been killed and more than 150 police have been wounded in days of violent clashes in the centre of Kiev. Ukrainian President Viktor Yanukovich has called for an emergency session of parliament to end the violent unrest.